1. Field of the Invention
The present invention relates to an improvement to and/or an accessory for a photometer adapted to detect luminescence from a liquid sample when luciferin or luciferase is added to a liquid solution containing adenosine triphosphate (ATP), an energy-storage compound that is present in all living cells. More specifically, the present invention relates to apparatus for maintaining constant the temperature of the liquid sample in a sample tube and for stirring and mixing the liquid sample in the sample tube when the tube is moved to a position within a reaction chamber of the photometer and beneath an opening through which a reagent is inserted into the sample tube.
2. Description of the Prior Art
Heretofore, photometer devices have been proposed having structure for moving a sample tube with a liquid sample therein from a position outside of a reaction chamber to an enclosed and darkened position within the chamber where a photomultiplier tube is positioned and where the tube is beneath a shielded opening at the top of the chamber through which a reagent such as luciferase can be inserted into the tube. An example of such a device is disclosed in U.S. Pat. No. 3,764,214.
In the previous devices it has been common to use some form of temperature control system for controlling the temperature of the liquid sample in the sample tube. See, for example, U.S. Pat. No. 3,917,404. As will be explained in greater detail hereinafter, the present invention provides a temperature control system which can be utilized in a standard rotatable sample tube carrier and which is believed to be simpler and less expensive than previous temperature control systems for photometers.
Also, it has heretofore been proposed to use a magnetic stirring device for stirring the liquid contents of the sample tube. Such a magnetic stirring device creates electrical interference which adversely affects the electronic circuitry of the photometer. As will be explained in greater detail hereinafter, the present invention provides a mechanical apparatus for stirring the sample tube after it is moved from a position outside the reaction chamber to a position within the reaction chamber and beneath the opening through which reagent is inserted into the sample tube.